===== Make the client in English =====
Go to the folder with the installed game itself and to the folder -> AIONINFINITE40 \ L10N \ RUS \ Data
Delete the data.pak file.

AFTER:
Extract files from archive.
Paste the new files (data.pak) into this folder (L10N\RUS\Data)
Now you can start the game.

P.S.
In the folder AIONINFINITE40\L10N\RUS\ - do not delete this folder!
Just do it as above!